1. Field of the Invention
The present invention is in the field of accumulator devices and is directed more particularly to a low cost, low pressure accumulator device and method of making the same.
2. The Prior Art
The use of accumulator devices for purposes of energy storage, pulsation dampening and the like is progressively increasing. Such devices typically are comprised of a pressure vessel having an oil port at one end communicated with a hydraulic line, and a gas charging valve at the other end, the interior of the vessel being divided into two discrete chambers in communication, respectively, with the gas charging valve and the oil port by a distensible bladder.
When gas under pressure is admitted through the gas charging valve, the bladder is distended into sealing relation of the oil port. When pressure in the hydraulic system exceeds the pressure in the gas chamber, fluids enter the oil port, further compressing the gas, with concomitant storage of energy in the gas or dampening of pulses.
When the pressure in the hydraulic system drops, such that the gas pressure again exceeds the oil pressure, the bladder expands, releasing energy to the hydraulic fluids.
Heretofore accumulator devices have been relatively expensive, in part by reason of the cost of casting or forging the pressure vessel, mounting a bladder assembly in the vessel, and closing the vessel with an end cap assembly carrying a gas charging port.
Generally, the cast or forged pressure vessels must be machined to provide threaded connections for facilitating mounting of the concomitantly threaded end cap.
Additionally, provision must be made for clamping or otherwise supporting a carrier ring bonded to the open mouth of the bladder portion.
In alternative constructions, the bladder portion includes a thickened rim surrounding the mouth, which rim is clampingly engaged between the elements of the pressure vessel which are threaded into position.
The various modes of fabricating and finishing the pressure vessel, supporting the bladder assembly therein and dependably sealing the vessel, as represented by U.S. Pat. Nos. 2345,124--Huber; 3195,576--Mercier; 3963,052--Mercier; 3918,497--Schoon; and 3792,721--Zahid, have materially increased the cost of manufacturing accumulator devices.
While it has been proposed to manufacture accumulator devices, and particularly devices intended to operate at relatively low pressures, of metal parts formed by spinning, etc., the problems inhering in dependably securing the parts together and effecting the desired seal have proven substantial. More particularly, while it has been proposed to connect, by welding operations, the bladder carrying components of a device to the interior of the pressure vessel and thereafter, by a further welding step, to complete the formation of the presure vessel, difficulties, particularly in heat dissipation, have resulted in an inordinate number of instances of failure of the bladder. The welding step has resulted in the conduction of heat to the bladder and/or to the junction between the retainer member for the bladder and the bladder, with frequent resultant failure.
Various attempts have been made to prevent overheating of the bladder in the course of welding, such attempts including the circulation of water against portions of the device to aid in conducting heat away from the bladder. However, no completely satisfactory system for reliably linking the elements of a thin-walled, relatively low cost pressure accumulator device by welding steps has heretofore been achieved.